Phosphorus Reduction Research Articles

Zirconium-Modified Attapulgite Composite for Phosphorus Removal and Algae Control in Lake Water

Phosphorus removal is critical for effective water treatment and the prevention of eutrophication. This study focuses on the modification of attapulgite, an economical clay material, with zirconium (Zr@ATP) to enhance its phosphorus adsorption capacity. Zr@ATP was comprehensively characterized, and its phosphorus-removal mechanisms were investigated. Additionally, its performance in water treatment was evaluated using a lake water-sediment system. Zr@ATP exhibited a high surface area of 329.29 m2/g. The static adsorption experiments revealed that Zr@ATP achieved a phosphorus-removal efficiency of 95.8% at an adsorbent dosage of 5 g/L. Kinetic studies indicated that the adsorption followed a pseudo-second-order model, with the primary mechanism being chemisorption via ion exchange. Application of Zr@ATP in a lake water-sediment system resulted in an 83.6% reduction in total phosphorus. The chlorophyll concentration significantly decreased from 32.33 μg/L to 8.56 μg/L, and the algal density decreased by 84.6%, effectively inhibiting algal growth. These results suggest that Zr@ATP is a promising adsorbent for sustainable phosphorus removal and eutrophication control in aquatic environments.

Dietary Protein Consumption Pattern in Hyperphosphatemia Management Among Haemodialysis Patients: A Cross-Sectional Study at Kenyatta National Hospital, Kenya

Poor nutrition status in haemodialysis patients is associated with high mortality rates. A low phosphorus diet is likely to compromise dietary protein intake and nutrition status in this population. This study evaluated dietary protein consumption pattern and nutrition status among forty out-patient haemodialysis patients from Renal Unit at Kenyatta National Hospital using cross-sectional study. The Chi-square test and Kruskal‒Wallis H test were used to determine relationship between variables. More than half (58%) of the patients were male. Study participants had a mean age of 45.4±14.7 years with the majority (40%) between 40-59 years. More than three quarters (88%) had poor nutrition status with more than a third (38%) severely undernourished. More than half of the patients (53%) had dialysed for a period of more than one year. Most of study participants consumed only five types of legumes. Yellow bean, butterfly Kenyan kidney bean, butterfly haricot bean, red kidney bean and green lentil were commonly consumed legumes; 2-4 times per week by 45%, 23%, 23%, 8% and 15% of the patients respectively. Beef was the most consumed animal protein by more than half (53%) of the patients in 2-4 times a week. Second most consumed animal protein was egg white at least 2-3 times a week. Majority of the patients (58%) had poor knowledge scores (<50 % score) on food phosphorus reduction food preparation procedures in protein rich foods. This study found high prevalence of poor nutrition status and inadequate consumption of dietary protein among haemodialysis patients. This study recommends nutrition education and counseling on locally available dietary proteins and their preparation in order to meet dietary protein requirements without risk of hyperphosphatemia

Efficacy and safety of sucroferric oxyhydroxide versus sevelamer carbonate: A systematic review and meta-analysis.

Phosphate binders are commonly used in patients receiving kidney replacement therapy (KRT), aiming to reduce and maintain serum phosphorus. Chronic kidney disease-mineral and bone disorder has been linked to reduced lifespan and worsened quality of life. This study aims to examine the efficacy and safety of sucroferric oxyhydroxide versus sevelamer carbonate in patients receiving KRT. The data sources examined were MEDLINE (PubMed), Scopus, and the Cochrane Central Register of Controlled Clinical Trials with a search deadline of October 2023. We examined randomized controlled trials that compared sucroferric oxyhydroxide versus sevelamer carbonate in the adult population receiving KRT. We performed a meta-analysis combining the data from trials, using R-studio. Inclusion criteria were met by five randomized trials. There was no statistically significant difference in the reduction of serum phosphorus between the two groups (MD: -0.07 mmol/L, 95% CI-random effects: -0.15 to 0.02). In the same line, a non-statistically significant difference was observed in serum i-PTH reduction between the two drugs (MD = -1.53 mg/dL, 95% CI = (-4.45, 1.4), p = 0.26, random effects model). No statistically significant difference was observed in all adverse events between the two groups (odds ratio: 1.11, 95% CI: 0.65-1.88, random effects model). Further analysis of gastrointestinal adverse events revealed that sevelamer carbonate increases gastrointestinal adverse events by up to 60% (odds ratio: 1.60, 95% CI: 1.31-1.97, common (fixed) effect model). This meta-analysis of randomized trials showed that both drugs, sucroferric oxyhydroxide and sevelamer equally and effectively controlled serum phosphorus levels, whereas sucroferric oxyhydroxide revealed a better profile in terms of gastrointestinal adverse events. Sucroferric oxyhydroxide is a valuable option for patients receiving KRT when sevelamer carbonate is more difficult to tolerate.

Application Research on the Use of Multiple Comparison Methods in The Evaluation of the Effectiveness of Total Nitrogen and Total Phosphorus Reduction Measures

With the problem of water pollution becoming increasingly serious, excessive discharge of nitrogen and phosphorus has become a key factor affecting water quality and ecological balance. In order to evaluate the effectiveness of different pollution reduction measures in total nitrogen and total phosphorus control, this study evaluates multiple best management practices (BMPs) using multiple comparison methods, in particular Tukey HSD testing. The results of the statistical analysis of the reduction effects of the different measures showed that all the treatment groups with measures were significantly better than the control group without measures. In particular, BMP 8, BMP 7 and BMP 6 showed the best reduction effects. This study not only provides a scientific basis for pollution control decisions, but also lays the foundation for follow-up research, highlighting the importance of multiple comparison methods in environmental science.

The Effects of Meander Reconnection and Deflector Installation on the Physicochemical Water Quality

ABSTRACTRiver restoration efforts are gaining momentum in response to the pressing need for resilient river systems, in light of escalating climate change impacts. However, achieving predefined restoration goals remains challenging due to insufficient understanding of river system responses. Of particular complexity is assessing the success of restoration measures on water quality, a critical abiotic factor in freshwater ecosystems. This study examined the impact of meander reconnection and deflector placement on water quality. Two distinct meander sections and a degraded section were meticulously sampled both upstream and downstream to assess impacts. The meander sections were reconnected using different approaches: one fully reconnected, receiving all discharge, and the other partially reconnected, receiving part of the discharge while maintaining the channelized trench. The results showed promising potential of reconnected meanders for mitigating phosphorus and carbon levels. However, the effectiveness of these improvements was compromised by deflector placement, which led to increased erosion and release of phosphorus bound to organic soil particles. Conversely, dissolved nutrients (e.g. nitrate, orthophosphate, DOC) exhibited no significant alterations, likely attributed to the absence of macrophytes and the limited extent of restorative actions, which currently do not increase water residence time sufficiently. Temporal trends revealed progressive reductions in carbon, phosphorus, and nitrogen levels suggesting that time is a crucial factor in restoration success, possibly due to soil stabilization. Seasonal dynamics also played a significant role, with discernible effects observed primarily during summer. This study underscores the importance of long‐term, watershed‐scale investigations that account for seasonal variability to fully understand the impacts of river restoration.

Mobilization of phosphorus in sediments of eutrophic lakes induced by elevated sulfate levels

Elevated sulfate levels in eutrophic lakes have been observed to induce the release of endogenous phosphorus. While previous studies have predominantly examined its impact on iron-bound phosphorus (FeP), the influence on organic phosphorus (OP), a crucial active phosphorus component in sediments, remains poorly understood. In this study, mesocosms were established with lactate supplementation and varying sulfate concentrations to explore sulfate reduction and its impacts on phosphorus mobilization in freshwater sediments. Lactate addition induced hypoxia and provided substrates, thereby stimulating sulfate reduction with a decline of sulfate levels, an increase of sulfide concentrations, and fluctuations of sulfate-reducing bacteria. Meanwhile, concentrations of total dissolved phosphorus and phosphate were dramatically promoted during lactate decomposition, with a higher sulfate concentration associated with greater phosphorus elevation, correlating with the decrease of total phosphorus in sediment. The increase in phosphorus of the overlying water was partly attributed to FeP release from the sediment, confirmed by a decrease in its sediment content. FeP release was ascribed to dissimilatory reduction of iron oxides or chemical reduction mediated by sulfides in anoxic sediments, leading to the desorption and subsequent release of phosphorus. Evidences included the proliferation of iron-reducing bacteria, a decrease in Fe(II) concentrations in sediment pore- water, and the continuous accumulation of solid iron sulfides in surface sediments. Furthermore, OP mineralization in sediment also contributed to the increase in phosphorus in water columns, confirmed by a reduction in its content and the abundance of fermentation bacteria in surface sediment. Notably, the decrease in OP content accounted for >80 % of the total phosphorus reduction in surface sediment in the end. Thus, sulfur cycling plays a critical role in iron and phosphorus cycling, significantly stimulating not only the mobilization of FeP but also OP in sediments, with OP mineralization potentially being the primary contributor to endogenous phosphorus release.

Long‐term comparison of targeted soil test values and crop removal as a phosphorus fertilization strategy in corn

AbstractFinding effective phosphorus (P) recommendation strategies to optimize corn (Zea mays L.) yield under varying yield levels and environmental conditions is continuously sought after. A 16‐year study was conducted in Concord, NE, on Nora silt loam soil initially measuring 16 ± 3 mg kg−1 Bray‐1 P. The study evaluated the impact of different P fertilization strategies on corn yield across various growing conditions (dry, normal, and wet years). Treatments included no P or N (NPNN), no P (NP), P applied at crop removal phosphorus (CRP), and maintaining soil P at 15 (B15), 30 (B30), and 45 (B45) mg kg−1 Bray‐1 P, with similar nitrogen (N) rates except for NPNN. Results showed a 25% and 33% reduction in soil test phosphorus (STP) for NPNN and NP treatments, respectively. The total P required by B30 and B45 treatments was 1.8 times more than that for CRP and B15. Although B30 and B45 treatments increased corn grain P concentration by 6%–12% compared to B15 and CRP, they did not increase yields in normal and dry years. The NP led to yield reductions of 9% and 12% in normal and wet years, respectively. In contrast, CRP achieved an 8% higher yield than B15 during wet years. Economic analysis revealed that B45 yielded a 56% higher net return in normal years, while CRP offered the highest return on investment (ROI) at 4.9. This study highlights the complexity of managing soil P under varying environmental conditions, emphasizing that while maintaining higher STP levels (B30 and B45) can enhance grain P concentration, it does not significantly boost yield and ROI compared to CRP and B15.

Nitrogen availability controls response of microcystin concentration to phosphorus reduction: Evidence from model application to multiple lakes

Microcystis blooms are a global contemporary problem and the mechanisms underlying strain-level ecology (e.g. toxigenic fraction) and toxin (microcystin, MC) production are not sufficiently understood. Recent research suggests that MC synthesis depends on the availability of nitrogen and light, and that they protect toxigenic cells against damage by H2O2. The non-toxigenic strains employ the alternative strategy of enzymatic degradation of H2O2. Thus, MC-producing cells may have an advantage at high nitrogen and light availability. A model based on this mechanism was able to reproduce the observed patterns of toxigenic fraction and MC concentration in Lake Erie. However, it is unclear if this mechanism also applies to other systems. We investigated this by modeling nine different cases (i.e. lakes, stations, years). The model can reproduce observed patterns (toxigenic fraction, concentration of MC, biomass, nutrients and if available H2O2) for all cases, which constitutes support for the proposed mechanism. To explore lake management, we simulated single and dual nutrient (i.e. nitrogen and/or phosphorus) reduction, which predicts two types of outcomes. For lakes with nitrogen limitation at some time during the blooming season (e.g. Lake Erie) a phosphorus only reduction does not reduce MC concentration proportionally and may even increase it. Reducing phosphorus lowers biomass, which increases nitrogen and light availability and raises MC production and toxigenic fraction. For lakes with replete nitrogen (e.g. Lake Taihu) MC concentration is predicted to decrease. Here, further nitrogen availability will not increase MC production. These results advance mechanistic understanding of Microcystis strain ecology and toxin production and provide guidance for management.

The benthic nepheloid layer in the offshore waters of the Great Lakes and its post-dreissenid disappearance

Prior to the appearance of Dreissena, pronounced benthic nepheloid layers (BNL) near the bottom characterized by elevated levels of both turbidity and total phosphorus (TP), were a consistent and extensive feature of the offshore, stratified waters of all the Laurentian Great Lakes, except Lake Superior. In recent (2010–2019) years, the BNL has disappeared from all areas except for central Lake Erie, where only a small decrease in bottom turbidity has occurred. All stratified regions which exhibited a pre-Dreissena BNL, including central Lake Erie, experienced substantial post-Dreissena reductions in near-bottom TP, although the forms of phosphorus (particulate or soluble) responsible for these reductions have varied from lake to lake. Notably, the arrival of Dreissena at offshore sites was not accompanied by an increase in soluble phosphorus. Initiation of changes in the BNL almost invariably preceded appearance of Dreissena in the offshore, suggesting both that dreissenid impacts on the reductions in the BNL were largely remote, and by extension that the source of the BNL was also at least in part remote. Previous researchers’ estimates of the importance of the benthic pool of phosphorus to offshore water column concentration suggest that the post-invasion reductions in bottom phosphorus during the stratified season could be contributing to the offshore oligotrophication of the lakes.

Quantifying the impact of damming on phosphorus reallocation: Finer particles offset the reduction in soluble reactive phosphorus (SRP) by decreasing suspended sediment concentration

In this research, an innovative approach to quantify the impact of damming on phosphorus (P) reallocation between suspended sediments (SS) and water was proposed. P allocation can be described by the surface complexation model, with the impact of damming quantified by four variables: P load, suspended sediment concentration (SSC), particle size, and pH. Iron/aluminium (Fe/Al) oxide-adsorbed P (Fe/Alo-P) was identified as the exchangeable P during adsorption/desorption equilibrium with a series of heterogeneous sediment samples from two large Asian rivers, the Mekong River and the Yellow River. In both rivers, the Fe/Alo-P concentration increased from the tail towards the dam of the reservoirs, primarily attributed to the decrease in particle size from the tail towards the dam of the reservoirs. The Fe/Alo-P concentration in the Lancang River was higher than that in the Yellow River, ranging from 14.5 to 119.9 mg kg−1 and from 14.5 to 22.1 mg kg−1, respectively. The soluble reactive P (SRP) concentration decreased with decreasing SSC, while finer suspended sediment particles containing more Fe/Alo-P greatly offset the reduction in SRP concentration. When the maximum Fe/Alo-P concentration in the finest particles of SS was assumed to be 100 mg kg−1, the P equilibrium concentration (ce) decreased from 0.028 mg L−1 to 0.008 mg L−1 when the SSC decreased from 64 g L−1 to 1 g L−1 for SS with a median grain size (D50) of 32 μm and an Fe/Alo-P concentration of 11 mg kg−1. However, ce increased from 0.008 mg L−1 to 0.021 mg L−1 when the D50 of SS decreased from 32 μm to 4 μm with an SSC of 1 g L−1 and an Fe/Alo-P concentration of 76 mg kg−1 for 4-μm SS. The SRP concentration is sensitive to the Fe/Alo-P concentration in SS, and the P allocation ratio between sediments and water is comparable.

Refeeding hypophosphatemia is a common cause of delirium in critically ill patients: A retrospective study

BackgroundThe purpose was to explore the correlation between refeeding hypophosphatemia and delirium and analyze the related factors in critically ill patients. MethodsWe conducted a retrospective review of critically ill patients admitted to Nanjing Drum Tower Hospital between September 2019 and March 2021. The patients were divided into delirium and nondelirium groups. Demographic data, underlying diseases, laboratory findings, comorbidities, nutritional intake and overall prognosis were collected and analyzed. ResultsIn total, 162 patients were included and divided into delirium (n = 54) and nondelirium (n = 108) groups. Serum phosphorus levels in the two groups decreased significantly in the first three days (P1, P2, P3) after nutrient intake compared with baseline before nutrient intake (Ppre). P1 and P2 were significantly lower in the delirium group compared to the nondelirium group. The maximum blood phosphorus reduction (Pmax) in the first three days after nutrient intake was significantly higher in the delirium group than in the nondelirium group. The time of Pmax in the delirium group was on the first day after nutrient intake. Multivariable logistic regression analysis identified starting route of nutrition and P1< 0.845 mmol/L as the independent predictors of delirium development in critically ill patients. ConclusionThe incidence of delirium in critically ill patients is high and associated with refeeding hypophosphatemia. Delirium may occur with serum phosphorus levels less than 0.845 mmol/L on the first day.

A novel strategy of bloom forming cyanobacteria Microcystis sp. in response to phosphorus deficiency: Using non-phosphorus lipids substitute phospholipids

Despite significant reductions in phosphorus (P) loads, lakes still experience cyanobacterial blooms. Little is known regarding cellular P regulation in response to P deficiency in widely distributed bloom causing species such as Microcystis. In this study, we investigated changes in P containing and non-P lipids contents and their ratios concomitantly with the determinations of expression levels of genes encoding these lipids in cultural and field Microcystis samples. In the culture, the content of phosphatidylglycerol (PG) decreased from 2.1 μg g-1 in P replete control to 1.2 μg g-1 in P-deficient treatment, while non-P lipids, like sulfoquinovosyldiacylglycerol (SQDG) and monogalactosyldiacylglycerol (MGDG), increased dramatically from 13.6 μg g-1 to 142.3 μg g-1, and from 0.9 μg g-1 to 16.74 μg g-1, respectively. The expression of the MGDG synthesis gene, mgdE, also increased under low P conditions. Significant positive relationships between soluble reactive phosphorus (SRP) and ratios of P-containing lipids (PG) to non-P lipids, including SQDG, MGDG and digalactosyldiacylglycerol (DGDG) (P < 0.05) were observed in the field investigations. Both cultural and field data indicated that Microcystis sp. might increase non-P lipids proportion to lower P demand when suffering from P deficiency. Furthermore, despite lipid remodeling, photosynthetic activity remained stable, as indicated by comparable chlorophyll fluorescence and Fv/Fm ratios among cultural treatments. These findings suggested that Microcystis sp. may dominate in P-limited environments by substituting glycolipids and sulfolipids for phospholipids to reduce P demand without compromising the photosynthetic activity. This effective strategy in response to P deficiency meant a stricter P reduction threshold is needed in terms of Microcystis bloom control.

Magnetic susceptibility and properties of Alisols under forest and crops in south Amazonas

Anthropic actions have motivated pieces of research on the impacted naturally poor soils of the Brazilian Amazon, requiring the use of diagnostic attributes that are increasingly specific to each environmental change. The use of magnetic proxies inherent in the soil may be the key to understanding the changes that occur in the soil and the environment. Therefore, this study aimed to characterize the physical, chemical and mineralogical properties of Alisols, in addition to determining the intensity and origin of the magnetic signal for future calibrations as an environmental proxy for monitoring soil fertility. One natural and three cultivated Alisols were sampled using systematic meshes in three layers: 0–5, 5–10 and 10–20 cm. The natural Alisol is a tropical forest and the agricultural ones refer to the cultivation of annatto, cupuaçu and guarana. A total of 192 samples/area were submitted to physical, chemical, mineralogical and magnetic susceptibility (MS) analysis. MS measured at low and high frequency and converted to specific mass (χlf and χhf), then descriptive, univariate and multivariate statistical analyzes were applied to the results. The conversion of the physically good and chemically poor and acidic natural Alisols to agricultural crops, caused an increase in the density and amplitude of the pH in water and Al3+ of the soil, plus a reduction in macroporosity, gravimetric humidity, available phosphorus and iron oxalate contents, and the incorporation of organic carbon in depth. All Alisols showed low χlf and χhf. However, χlf values decreased in depth for cultivated Alisols (0.53–0.26 x 10−6 m3 kg−1), whereas, for natural Alisol, these values tended to increase towards the subsurface (0.21–0.23 x 10−6 m3 kg−1). Nevertheless, the value of χlf and χhf were highly representative within the cultivation areas, which was characterized as a suitable proxy to monitor the fertility of the Alisols in the Amazon region.

Cultivation of a naturally resilient Chlorella sp.: A bioenergetic strategy for valorization of cheese whey for high nutritional biomass production

This study investigated Chlorella's capacity to treat cheese whey (CW) effluent and produce a high-nutritional value biomass, by using a systematic sequential experimental design. Physicochemical analysis of CW revealed its high pollution load, characterized by elevated levels of lactose, phosphorus, and nitrogen, as well as high turbidity due to the presence of whey solids. Screening experiments demonstrated that trace mineral addition and continuous air supply are essential factors for Chlorella biomass production in CW (>800 mg·mL−1). Furthermore, whey solids did not hinder Chlorella growth, with notable biomass production observed even in undiluted CW, demonstrating this microalga's ability to adapt metabolically to the complex environment. Laboratory-scale photobioreactor experiments confirmed Chlorella's ability to produce biomass in CW, outperforming controls (>800 mg·mL−1). Bioremediation potential assessment exhibited significant reductions in organic pollutants (>14 g·L−1 COD), nitrogen (>400 mg·L−1), phosphorus (>140 mg·L−1) and sodium (>650 mg·L−1). CW solids were also removed with Chlorella harvesting (>99 %). Harvested algal biomass was enriched with proteins (>40 g·100 g−1), polyunsaturated fatty acids (>9 % TFA) and pigments, offering potential applications in nutraceutical and pharmaceutical industries. Overall, this study highlights Chlorella's efficacy in CW treatment and biomass valorization, offering a sustainable solution for dairy wastewater management while producing valuable resources.

Improving well-being and enhancing awareness in patients undergoing hemodialysis through the person-centered IARA model: an exploratory study.

Chronic kidney disease (CKD) globally represents a significant health challenge, particularly among patients undergoing chronic hemodialysis. A careful nutritional and pharmacological prescription plays a key role in the effective management of these patients to optimize serum electrolytes, such as potassium, phosphorus, and protein intake. Furthermore, these patients can suffer psychological distress due to dietary restrictions and tight medication schedules. The present study explores the effectiveness of the person-centered IARA model in improving physiological markers and quality of life in CKD patients undergoing hemodialysis treatment. To demonstrate the effectiveness of the IARA model, 60 patients (M = 40; F = 20; 60.5 ± 9.9 years) undergoing thrice-weekly hemodialysis sessions were enrolled and randomly and blindly assigned to the Control or IARA group. The reduction in abnormal blood potassium, phosphorus, and total protein levels was investigated, alongside the psychological state through the SF-12 questionnaire. Preliminary findings showed a discernible reduction in the frequency of abnormal blood K (> 5.0 mmol/L) and P (> 4.5 mmol/L) levels in the IARA group compared to the Control group. In particular, such reductions were approximately 40% for K (OR = 0.57; 95% CL = 0.23/1.46) and about 15% for P (OR = 0.86; 95% CL = 0.27/2.74). A similar tendency was also observed for patient fluid intake during each hemodialysis session, with the frequency of higher-risk patients in the IARA group being 50% lower (OR = 0.50; 95% CL = 0.07/3.79) than that of the Control group. Although preliminary findings from this study suggest that the IARA model may have a positive effect on CKD patients' subjective wellbeing and quality of life (QoL), further research is needed to understand the long-term impact of the IARA intervention.

Strawberry Yield Improvement by Hydrogen-Based Irrigation Is Functionally Linked to Altered Rhizosphere Microbial Communities.

Molecular hydrogen (H2) is crucial for agricultural microbial systems. However, the mechanisms underlying its influence on crop yields is yet to be fully elucidated. This study observed that H2-based irrigation significantly increased strawberry (Fragaria × ananassa Duch.) yield with/without nutrient fertilization. The reduction in soil available nitrogen (N), phosphorus (P), potassium (K), and organic matter was consistent with the increased expression levels of N/P/K-absorption-related genes in root tissues at the fruiting stage. Metagenomics profiling showed the alterations in rhizosphere microbial community composition achieved by H2, particularly under the conditions without fertilizers. These included the enrichment of plant-growth-promoting rhizobacteria, such as Burkholderia, Pseudomonas, and Cupriavidus genera. Rhizobacteria with the capability to oxidize H2 (group 2a [NiFe] hydrogenase) were also enriched. Consistently, genes related to soil carbon (C) fixation (i.e., rbcL, porD, frdAB, etc.), dissimilar nitrate reduction (i.e., napAB and nrfAH), and P solublization, mineralization, and transportation (i.e., ppx-gppA, appA, and ugpABCE) exhibited higher abundance. Contrary tendencies were observed in the soil C degradation and N denitrification genes. Together, these results clearly indicate that microbe-mediated soil C, N, and P cycles might be functionally altered by H2, thus increasing plant nutrient uptake capacity and horticultural crop yield.

Black Sea Eutrophication Comparative Analysis of Intensity between Coastal and Offshore Waters

Eutrophication, driven by excessive nutrient enrichment from sources like agricultural runoff, industrial discharge, and urbanisation, has severely impacted the Black Sea since the 1980s. This study aimed to assess eutrophication dynamics in the Romanian Exclusive Economic Zone from 2020 to 2022 using the Black Sea Eutrophication Assessment Tool (BEAST), an integrated approach to the causes and effects of eutrophication. Data were collected from 68 stations during five oceanographic expeditions, analysing 617 water samples for nutrients, chlorophyll a, zooplankton species Noctiluca scintillans, and dissolved oxygen. Additionally, 179 zoobenthic and 251 phytobenthic community samples were collected. The results indicate that coastal waters exhibit higher nutrient levels and algal blooms compared to offshore waters, necessitating significant reductions in nutrient concentrations to achieve good environmental status. In transitional waters, within the Danube Delta Biosphere Reserve, a 55% reduction in inorganic phosphorus and a 43% reduction in inorganic nitrogen concentrations are required, while coastal waters need reductions of 38% and 37%, respectively. The study highlights the need for improved wastewater treatment, stricter agricultural runoff controls, and continuous monitoring. Effective ecosystem-based management strategies, integrated coastal zone management, and international cooperation are essential to mitigate eutrophication and promote the long-term health of the Black Sea ecosystem.

Microbial succession and enrichment of antibiotic resistance genes during algal-bacterial biofilm purification of aquaculture wastewater

This study involved the establishment of algal-bacterial biofilms on the surface of carbon fiber-based artificial aquatic plants, utilizing algal-bacterial symbiosis for the purification of aquaculture wastewater. The algae-bacteria consortium exhibited strong photosynthetic activity, as indicated by the chlorophyll a + b content (0.918 ± 0.029 mg/g carbon fiber (CF)). Particularly, during the initial 7 days, algal-bacterial biofilm displayed robust water purification activity and capacity, with a significant reduction in total phosphorus (TP) of 39.44 % ± 2.43 % observed. The microbial community of the biofilm was diverse, primarily dominated by Proteobacteria, Cyanobacteria, Actinomycetota, and Planctomycetota. Among these, Proteobacteria were in the highest abundance ranging from 39.18 % to 40.61 %. Changes in Cyanobacteria, driven by nutrient level alterations, not only impacted species abundance but also posed a risk of promoting the spread of antibiotic resistance genes (ARGs). Through the complex interactions among biological communities, 15 types of ARGs have been enriched on the algal-bacterial biofilm, among which Multidrug, Bacitracin, Aminoglycoside, and Glycopeptid have a higher abundance. Contigs and network analysis indicate that Nannocystis, Sphingorhabdus, and Polynucleobacter are the key hosts and it is found that their abundance will increase during the purification of water quality by the algal-bacterial biofilm. This study highlighted the risk of ARG transmission in aquaculture effluent treatment with algal-bacterial biofilms.

Molecular-strain induced phosphinidene reactivity of a phosphanorcaradiene

Phosphanorcaradienes are an appealing class of phosphorus compounds that can serve as synthons of transient phosphinidenes. However, the synthesis of such species is a formidable task owing to their intrinsic high reactivity. Herein we report straightforward synthesis, characterization and reactivity studies of a phosphanorcaradiene, in which one of the benzene rings in the flanking fluorenyl substituents is intramolecularly dearomatized through attachment to the phosphorus atom. It is facilely obtained by the reduction of phosphorus(III) dichloride precursor with potassium graphite. Despite being thermally robust, it acts as a synthetic equivalent of a transient phosphinidene. It reacts with trimethylphosphine and isonitrile to yield phosphanylidene-phosphorane and 1-phospha-3-azaallene, respectively. When it is treated with one and two molar equivalents of azide, iminophosphane and bis(imino)phosphane are isolated, respectively. Moreover, it is capable of activating ethylene and alkyne to afford [1 + 2] cycloaddition products, as well as oxidative cleavage of Si–H and N–H bonds to yield secondary phosphines. All the reactions proceed smoothly at room temperature without the presence of transition metals. The driving force for these reactions is most likely the high ring-constraint of the three-membered PC2 ring and recovery of the aromaticity of the benzene ring.

Efficiency of Nitrogen Fertilization in Millet Irrigated with Brackish Water

Nitrogen fertilization can provide greater nutritional support and mitigate salt stress in the millet crop. The aim of this study was to evaluate the physiological responses and agronomic performance of millet crop subjected to nitrogen fertilization and irrigation water salinity. The study was carried out in a greenhouse, using a completely randomized design in a 5 × 2 factorial scheme, with four replications, with five doses of nitrogen (40; 60; 80; 100 and 120 kg ha−1 of N), and two levels of electrical conductivity for the irrigation water: 0.3 and 4.0 dS m−1. We concluded that salt stress increased leaf sodium levels and had a negative impact on stalk and panicle dry mass, leaf gas exchange, mineral element concentrations (K, P, and Ca), and water use efficiency. The use of lower-salinity water associated with increased nitrogen fertilization provides greater stalk and panicle dry mass, photosynthesis, water use efficiency, chlorophyll index, leaf potassium concentration, and biomass production. The adverse effects of salt stress were evident in decreased transpiration and stomatal conductance, alongside reductions in leaf phosphorus and calcium levels, coupled with elevated leaf sodium concentrations, particularly as nitrogen fertilization rates increased in potted millet plants. These findings offer insights for devising strategies aimed at mitigating the detrimental effects of salt stress on millet plant nutrition through targeted nitrogen fertilization approaches.